(Bloomberg Opinion) -- Just when you thought it was safe to get back in the water, a flood of news stories appear touting fears that great white sharks will start appearing off the coast of Cornwall in the UK as climate change warms the ocean. I'm more concerned about the sharks we already have.
Once a rare sight, great white sharks have started gathering in huge numbers in the North Atlantic, hunting in the shallows along the beaches of New England in the US. One possible explanation for the increase: The gray seal population — a great white's favorite meal — is surging, thanks to the 1972 Marine Mammal Protection Act which made it illegal for fishermen to cull them. Having almost entirely retreated from Cape Cod by the early 1960s, pupping colonies were reestablished in the area in the 1990s, and seal numbers had recovered to more than 30,000 by 2017. The predators themselves are also benefiting from protection laws introduced in recent years. It's a conservation success story worth celebrating.
If great whites are appearing in the North Atlantic on the US side of the ocean, why not this side? Seals are plentiful around the UK coast, and the water temperature is hospitable. Their ongoing absence is a mystery, according to shark experts. “Never say never, but it's a shame that whenever anybody does claim to see one, they don't seem to have their phone on them,” Paul Cox, chief executive officer of charity Shark Trust, told me.
The most dangerous thing you're likely to encounter in British waters is raw sewage. And more important than hunting for great whites is figuring out how climate change is affecting sharks that already make their home in UK waters.
More than 40 species hang out in British seas, roughly 21 of which are year-round residents . From flat-bodied angelsharks and porbeagles to spotty nursehounds and enormous basking sharks — gentle filter-feeders that would dwarf a great white — there's incredible diversity. We've even got Greenland sharks, which have the longest known lifespan of any vertebrates. One study carbon-dated the eyes of Greenland sharks; the largest, a five-meter (16.4-feet) female, was between 272 and 512 years old. Unfortunately, more than 50% of the UK shark population is under threat.
The main challenge globally to sharks is overfishing, when stocks are plundered beyond the breeding population's ability to recover. Sharks are vulnerable to targeted fishing as well as accidental bycatch, where they get trapped in nets intended to gather other fish. Climate change is an emerging threat, affecting the resilience of marine populations already stressed by fishing activity.
Around the UK, there's evidence that warmer waters are already leading to redistribution of our marine creatures. Animals that can't easily migrate such as plankton, kelp or limpets, stop being able to breed or die off in the warmer waters, being replaced by species that prefer higher temperatures. Fish that can move head further north to either find water that better suits their temperature preferences or to find prey.
In the southern North Sea, an area which has warmed rapidly, a study examining decades of data found a major shift, as larger species have disappeared and been replaced by smaller ones. While most declines could be linked to fishing, the starry ray, a close relative of sharks, prefers cooler waters and so recent warming may have driven it away from the area. Meanwhile, other fish species are moving in, with tuna, anchovies and John Dory turning up in British waters more often.
The study predicts that northwestern European waters are likely to become more suitable for species such as European seabass, sardine and sole, but less hospitable for halibut, Atlantic cod and haddock, among others. That has implications for the fishing industry, with the potential to spark some diplomatic spats.
Climate change is also messing with our attempts to protect sharks and other threatened species, given the unprecedented changes it's inflicting on the seas. “We've always managed the ocean as if it's static,” says Matt Frost, head of research organization Plymouth Marine Laboratory's international office. That's no longer a workable approach. For example, if a marine-protected area — a zone which limits human activities to safeguard rare and threatened species and habitats — is in place to shelter a specific fish but that fish moves north from that location, then what's the point of the zone? Frost and his colleagues are extolling “climate-smart MPAs” in which borders are revisited in order to respond effectively to changes.
Maybe great whites will eventually establish themselves off the coast of St. Ives. But spare a thought for the enigmatic species already here that we might soon lose.
More From Bloomberg Opinion:
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This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.
Lara Williams is a Bloomberg Opinion columnist covering climate change.
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